1. Technical Field
The present invention relates generally to a baghouse, a filter assembly for use in the baghouse and a method of installing the filter assembly in the baghouse. In particular, the present invention relates to a relatively long multi-piece filter assembly having pleated filter elements.
2. Description of the Prior Art
Continuous emphasis on environmental quality results in ever-increasing regulatory control on pollutants and emissions throughout the world. Much of the regulatory control is focused on reducing pollutants and emissions from certain industrial plants, such as power plants and metal production plants. A known technique to control pollutants and emissions from industrial plants is to separate undesirable particulate matter carried in a gas stream by fabric filtration. Such fabric filtration is accomplished in a dust collection apparatus known in the industry as a xe2x80x9cbaghouse.xe2x80x9d
The baghouse typically includes a housing divided into two plenums by a tubesheet. One plenum is a xe2x80x9cdirty air plenumxe2x80x9d which communicates with an inlet and receives xe2x80x9cdirtyxe2x80x9d or particulate laden gas from a source at the plant. The other plenum is a xe2x80x9cclean air plenumxe2x80x9d which receives cleaned gas after filtration and communicates with an outlet to direct cleaned gas away from the bathhouse. A plurality of relatively long cylindrical fabric filters, commonly called xe2x80x9cbags,xe2x80x9d are suspended from the tubesheet in the dirty air plenum. Each bag is installed over a cage and has a closed lower end. The cage may be in two or more pieces. Each bag is mounted to the tubesheet at its upper end to hang vertically in the dirty air plenum. The upper end portion of the bag is open and the interior of each bag is in fluid communication with the clean air plenum.
In operation, particulate laden gas is conducted into the dirty air plenum. As the particulate laden gas flows through the baghouse, the particulates carried by the as engage the exterior of the fabric filter bags and accumulate on the fabric filter bags or arc separated from the gas stream and fall into an accumulator chamber at the lower portion of the dirty air plenum. Cleaned gas then flows through the fabric filter bags, into the interior of the fabric filter bags, into the clean air plenum and through the outlet. Although many bag,houses are made according to this basic structure, there may be numerous operational and structural differences among baghouses.
There is interest in replacing known fabric filter bags with pleated element filters to increase the effective filtering area while occupying the same space, or less, within the baghouse as the known fabric filter bags. However, certain barriers to easy replacement of fabric filter bags by pleated element filters exist. In some baghouse designs, the fabric filter bags can have a length of about four meters. The clean air plenum often has a clearance height that is substantially less than four meters, for example, about one and a half meters. It is generally not a problem to install fabric filter bags in the baghouse since the fabric filter bags are foldable, flexible and non-rigid. A relatively lone and rigid pleated element filter cannot be installed without considerable manipulation if it can be installed at all, even if the baghouse has a roof with a portion that can be moved to a position which provides access to the clean air plenum. Not all baghouses have such a movable roof.
In order to occupy the same space within the baghouse as a fabric filter bag, the length of the pleated element filter would be relatively long and can be up to about four meters in length or more. This presents a problem for filter manufacturers because there are limits as to the width of the filter media that can be pleated with current production machinery to provide such a long, filter. The current production machinery used to pleat filter media typically cannot accommodate continuous filter media more than about two meters in width. Such a long filter would also be relatively difficult to handle and transport.
If the more efficient pleated element filter is desired, the majority of the filter must be capable of being inserted through an opening in the tubesheet from the clean air plenum. If known, relatively short, pleated element filter structures are used and are axially connected together, more problems can arise. Any structure used to connect known pleated element filter structures together must be strong enough to carry the load of the filter when it has particulates accumulated on it and fit through an opening in the tubesheet. Furthermore, a potting material, such as silicone or polyurethane, is typically used to hold a pleated element in a known filter structure and connect other structure of the filter together. This potting material has limited ability to carry load. The weight of filters supported by the potting material is relatively large and can exceed the potting material""s ability to carry sufficient load. For example, if a xe2x80x9ccleanxe2x80x9d filter having a pleated element and a length of about four meters weighs twenty pounds, it is estimated that particulates which accumulate on the pleated element could add 200 to 300 pounds to the weight of the filter structure.
It is, thus, seen that using pleated element filters in baghouses is very desirable. Accordingly, there is a need in the industry for improvements in filter structure and installation techniques.
The present invention is directed to an industrial baghouse, a relatively long filter assembly for use in the baghouse and a method of installing the filter assembly in the baghouse. The filter assembly of the present invention provides a relatively large filtration area for the space occupied. The filter assembly of the present invention can replace fabric filter bans in existing baghouses or be specified in new baghouses to take advantage of the filter assembly""s relatively large filtration area and ease of handling.
The baghouse of the present invention includes a housing that is divided into first and second plenums by a tubesheet. The tubesheet has a substantially planar portion with a plurality of opening is extending through the planar portion. The first plenum has a first dimension taken in a direction normal to the planar portion of the tubesheet. The second plenum has a second dimension taken in a direction normal to the planar portion of the tubesheet. The second dimension is greater than the first dimension.
The baghouse includes a plurality of filter assemblies supported by the tubesheet at their upper ends. Each filter assembly is adapted to hang in a substantially vertical direction. Each filter assembly has a first filter portion with a first attachment at a first open end. The first attachment is adapted to mount the first filter portion to the tubesheet at a location adjacent to an opening in the tubesheet. The first attachment supports at least a portion of the first filter portion in the second plenum and permits fluid communication between the interior of the first filter portion and the first plenum. A tubular member is fixed to and extends from the first attachment. A pleated filter element is disposed adjacent to the tubular member for support. A second attachment is fixed to the tubular member at a second and of the first filter portion. The second attachment defines an opening at the second end of the first filter portion through which fluid may flow. The tubular member is fixed to the first and second attachments with sufficient strength to support the weight of at least one other filter portion.
A second filter portion includes a third attachment at a first end to define an opening through which fluid may flow. A tubular member is fixed to and extends from the third attachment. A pleated filter element is disposed adjacent to the tubular member for support. A plate is located at a second end of the second filter portion and defines a closed end of the second filter portion.
A connection device sealingly connects the second attachment of the first filter portion to the third attachment of the second filter portion to enable fluid communication between the first and second filter portions. The connection device has a strength sufficient to support the weight of filter portions located on a side of the connection device opposite the first attachment of the first filter portion.
The filter assembly has a length greater than the first dimension of the first plenum. At least one of the first and second filter portions has a length in the range of one meter to three meters. The first filter portion also includes a portion adapted to extend through a respective opening in the tubesheet when the filter assembly is mounted to the tubesheet. The tubular member in at least one filter portion is welded, riveted or fastened to at least one of the attachments.
The connection device has a size capable of fitting through the opening in the tubesheet. The connection device comprises a clamping mechanism. The clamping mechanism includes portions movable between an unclamped position and a clamped position in a plane extending substantially normal to a longitudinal central axis of the filter assembly. A gasket is locatable between a surface of the clamping mechanism and at least one of the second attachment of the first filter portion and the third attachment of the second filter portion. The connection device may comprise a threaded connection. A compressible gasket is locatable between the second attachment of the first filter portion and the third attachment of the second filter portion to compress as the filter portions are connected together.
An alternative connection device has a connection tube extending from a collar formed on the connecting, end of a first filter portion. A groove is formed around the connection tube. The opposing filter portion has a flexible connection sleeve having a tongue corresponding to the groove of the connection tube. When the connection tube is inserted within the flexible connection sleeve, the tongue is seated within the groove. In this position, the rim of the connection sleeve contacts the end of the opposing filter portion and forms an air tight seal therebetween.
The filter assembly may include a third filter portion with attachments at opposite open ends fixed to a tubular member supporting a pleated filter element. The tubular member is fixed to the attachments with a strength sufficient to support the weight of at least one other filter portion. The third filter portion is adapted to be located between and connected to the first and second filter portions by a pair of connection devices. Each connection device sealingly connects an attachment of one filter portion with an attachment of an axially adjacent filter portion to enable fluid communication between the connected filter portions. Each connection device has a size capable of fitting through the opening in the tubesheet and a strength to support the weight of at least one other filter portion located on a side of the connection device opposite the first attachment of the first filter portion.
The method of the present invention is directed to installing a relatively long filter assembly in a baghouse. The baghouse is divided into first and second plenums by a substantially planar tubesheet. A plurality of openings extend through the tubesheet. The first plenum has a first dimension taken normal to the tubesheet. The second plenum has a second dimension taken normal to the tubesheet. The second dimension is greater than the first dimension. At least one filter assembly is adapted to be supported mostly in the second plenum and hangs in a substantially vertical direction.
The method includes the steps of providing a first filter portion with a first attachment at a first end. A tubular member is fixed to and extends from the first attachment. A pleated filter element is disposed about the tubular member for support. A second attachment is fixed to and extends from the tubular member at a second open end of the first filter portion through which fluid may flow.
The method also includes the step of providing a second filter portion with a third attachment at a first open end of the second filter portion through which fluid may flow. A tubular member extends from the third attachment. A pleated filter element is disposed about the tubular member for support. A plate is located at a second end of the second filter portion to define a closed end of the filter assembly.
The method further includes connecting the second attachment of the first filter portion to the third attachment of the second filter portion with a connection device. The connection device is constructed to have sufficient strength to support the operational weight of filter portions located on a side of the connection device opposite the first attachment of the first filter portion. The filter assembly and connection device may then be moved through the opening in the tubesheet.
The connecting together step further includes the step of providing a filter assembly having a length greater than the first dimension of the first plenum when the first and second filter portions are connected together. The method also includes the step of mounting the first attachment of the first filter portion to the tubesheet of the baghouse to support the filter assembly. The connecting together step includes moving portions of a clamp in a plane extending normal to the longitudinal central axis of the filter assembly to a clamped position against the second and third attachments. The connecting together step may include threading the third attachment into the second attachment.